vwlfan:
It is rare for a truck to have both a front mount and a mid mount pump, could you send more pictures of the mid mount pump? The petcock that you mention could be to add water from the fire pump to the raditor. Good if you are overheating, bad in that you loose your antifreeze strength. The engine cooler has an internal coil so the pump water and engine coolent dont mix. If a hole were to rust through the coil again the waters can mix. I have a manual somewhere on those pumps if interested.
Tim
